Hi, I would love to work on this project.
I have worked with both front-end and back-end technologies and programming languages - PHP, jQuery, HTML, Javascript, MySQL - just to name a few.
The calculator itself is a front-end combination of HTML, CSS and Javascript(jQuery), the PDF could be generated both on back- and front-end depending on your requirements.
The more of the calculator on front-end, the better, since you can browse to the page with data connection, then when the page has loaded, turn it off, since Javascript runs on your browser and doesn't require data connection to run, and when you're online again, upload the results generated with Javascript to a database.
I would recommend implementing a database into your calculater from the beginning since it really makes things easier, you could keep all the tests in a database in a JSON dump and easily export all the data and import it somewhere else, I could also write some PHP code that would make exporting a lot easier.
Feel free to contact me to discuss more details.
Best regards,
Kauri